1. Field of the Invention
The invention relates to a cooling device which has a cooling nozzle for introducing a coolant through the tube member used in a forcibly cooled casting and which is cast as part of the casting, said cooling nozzle being fit to the tube member accurately and tightly, and a method for its assembly.
In general, for the production of an aluminum alloy casting such as an aluminum cylinder head that is free of casting defects, it is desirable that the poured metal solidifies rapidly and that the solidification be unidirectional. In gravity casting and low pressure casting in the prior art, metallic molds have been water-cooled or air-cooled to promote fast metal solidification. For this type of mold cooling it is required to control the metallic mold temperature relatively rigorously in order to avoid over-cooling in the mold which may cause the metal poured in the mold cavity to be insufficiently fluid. Such control requires relatively sophisticated technology because of the periodic variations in the mold temperature as the casting cycle proceeds. Further, the cooling device provided in the metallic mold makes mold construction more complicated, giving rise to a higher metallic mold cost.
For the desired unidirectional solidification of the metal poured in the mold, the position and the shape of the riser, its volume, etc. are selected empirically, but such selection is limited by the shape of the casting in the mold. It is therefore sometimes impossible to achieve unidirectional solidification by the riser alone. In addition, in the prior art the speed of solidification of the poured metal in the mold is not fast enough in general and castings produced are not strong enough.
2. Description of the Related Art
Due to the above mentioned disadvantages, the Applicant has proposed a forcibly cooled casting method in which a tube member is placed in the cavity of a mold and the molten metal poured in the cavity incorporates therein the tube portions in contact with the hot metal. The poured metal is then cooled by passing a coolant through the tube so that the metal solidifies faster. This forcibly cooled casting method therefore uses the tube member which will be incorporated into a completed casting in order to cool the poured metal. In this method it may be possible to bring about unidirectional solidification in the metal near the outer face of the tube with the excellent advantage of improved strength in the casting accompanied by a shortened casting cycle time.
It is necessary, however, in the above mentioned forcibly cooled casting method, to position said tube member in either a sand mold or a metallic mold before casting, and when the tube member is exactly positioned in the mold at a specified position, connecting to the tube member a nozzle for injecting a coolant into the tube member, but the above method provides no specific method for such steps.